1. Field of the Invention
This disclosure relates to negative active materials for rechargeable lithium batteries, methods of preparing the same, and rechargeable lithium batteries including the same.
2. Description of the Related Art
Rechargeable lithium batteries have recently drawn attention as power sources for small, portable electronic devices. They use organic electrolyte solutions and therefore have twice the discharge voltage of conventional batteries using alkaline aqueous solutions. Accordingly, they have high energy density.
For the positive active material of a rechargeable lithium battery, chalcogenide compounds (i.e., composite metal oxides such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1)), and the like have been used.
For the negative active material of a rechargeable lithium battery, various carbon-based materials capable of intercalating and deintercalating lithium ions have been used, for example, artificial graphite, natural graphite, and hard carbon. Graphite increases discharge voltage and energy density of the battery because it has a low discharge potential of −0.2V (compared to lithium). A battery using graphite as the negative active material has a high average discharge potential of 3.6V and good energy density. Furthermore, among the aforementioned carbon-based materials, graphite is used most often since graphite yields better battery cycle life due to its good reversibility. However, graphite active materials have low density (i.e., a theoretical density of 2.2 g/cc) and therefore yield low capacity in terms of energy density per unit volume when used as the negative active material. Further, graphite causes swelling or capacity reduction when the battery is misused or overcharged and the like, because graphite is likely to react with the organic electrolyte at high discharge voltages.